1. Field of the Invention
This invention relates to electrosurgical electrode instruments for surgical cutting of body tissue.
2. Technical Background
Electrosurgical instruments are used extensively in surgical practice and the advantages to their use over conventional non-electrical surgical instruments are well recognized in the practice. A common approach taken in the art of electrosurgery that is effective for both cauterizing and cutting tissue entails the use of a monopolar circuit. A monopolar circuit is composed of an electrosurgical generator with two outlet connections: an active and a dispersive. The dispersive outlet connects to a dispersive pad which is attached to a patient's body. The electrosurgical generator sends high frequency electrical energy through the patient's body by means of the dispersive connection. The active connection is connected to an electrode which is then placed in proximity to or in contact with the body. Thus, the electrical energy present in the body is concentrated to those specific areas in proximity to the electrode. Those cells of the body thus exposed to the concentrated electrical energy are heated and then exploded by sparks arcing from the electrode to the cells. In this manner, the circuit is completed and, depending on further techniques, cauterization or cutting is achieved.
The shape and size of the electrode may vary depending on the purpose of the surgery. Commonly found in the surgical practice are electrosurgical instruments that utilize thin, wire electrodes. Typically, the wire electrodes are configured into needle or loop shapes. Both the needle and the loop electrodes are efficient cutters because their thinness allows the surgeon to concentrate the electrical energy to a very limited region of body tissue, thus fully utilizing the energy in the cutting process and preventing any unnecessary exposure to the electrical energy where cutting or burning of tissue is not desired. The principles that govern the electrosurgical cutting process are well known and the observation that thin wire electrodes are the best cutters is not a surprising conclusion to any knowledgeable practitioner.
However, the wire electrodes are limited in their cutting performance due to their lack of mechanical rigidity and their general fragile nature. This is especially true when the electrodes become hot during the surgical cutting process. Furthermore, it is often desirable for the surgeon to use the cutting electrode, without current applied, as a mechanical tool to separate tissues (i.e., cold or mechanical dissection) that are adjacent to each other but which should not be exposed to the electrical energy of electrosurgical cutting. Naturally, the thin electrodes function poorly in mechanically separating body tissue because they lack sufficient mechanical reinforcement to effect proper dissection.
An electrosurgical instrument that is conveniently used both for electrosurgical cutting and mechanical dissection is the paddle electrode. This elongated, flat electrode has the mechanical strength to allow mechanical dissection and is able to create sufficient current concentration on its edges to accomplish good electrosurgical cutting. However, compared to a needle or wire loop electrode, the paddle electrode is a less efficient cutter because much of the high frequency electrical energy supplied by the electrosurgical generator flows to the body tissue through the sides of the paddle electrode where no exposure or cutting activity is desired. In some circumstances, the current flowing through the sides of the paddle electrode may have a beneficial effect in cauterizing the wound created in cutting through the tissue. However, in most cases, it is a wasteful use of current resulting in an extra burden for the electrosurgical generator and requires a larger power setting of the generator to accomplish the cut. Using a paddle electrode also frequently results in thermal damage to the tissue along the cut and in troublesome sticking of tissue to the sides of the paddle. Nevertheless, the paddle electrode has the advantages of superior mechanical strength and a flat shape that acts as a rudder giving the surgeon a better ability to guide the electrode along a straight or smooth curved line.
One attempt to solve the side conduction problem of the paddle electrode has been to coat the sides of the paddle with plastic, typically Teflon, which diminishes the current conducted out the side and prevents sticking of the tissue to the paddle electrode. This solution is only partially successful because at the high frequencies used for electrosurgery, there is substantial current that is capacitively coupled from the metal of the paddle, through the plastic coating, and to the body tissue. Thus, a more successful and permanent solution has yet to be realized.
From the foregoing, it will be appreciated that it would be an advancement in the art to provide an improved electrosurgical cutting device which realizes the advantages of the wire electrode and paddle electrode and at the same time eliminating their disadvantages. Specifically, it would be an advancement in the art to provide an electrosurgical cutting device which concentrates the electrical energy to a limited area of body tissue, yet has sufficient mechanical rigidity to allow improved cutting performance and to permit mechanical dissection. Yet another advancement in the art is to provide a device with the above features which is simple and economical to manufacture.
Such an electrosurgical cutting device is disclosed and claimed herein.